MemoryLeakByEvents.js

const EventEmitter = require('events');

const manager = new EventEmitter();

class A {
    constructor(event) {
        event.on('event1', this.doSomething);
    }

    doSomething(data) {
        console.log(`Do for ${data}`);
    }
}

var aInstance = new A(manager);

manager.emit('event1', 'first');

aInstance = new A(manager);

manager.emit('event1', 'second');